Renal impairment associated with diabetes in the elderly.

OBJECTIVE: To characterize renal impairment associated with diabetes in older adults by serum markers of glomerular filtration rate and microalbuminuria tests. RESEARCH DESIGN AND METHODS: The study population consisted of 187 diabetic and 1,073 nondiabetic subjects (age range 64-100 years) participating in a cross-sectional, population-based survey in southwestern Finland. Renal function was estimated by serum cystatin C (Cys C), serum creatinine (Cr), and the urinary albumin-to-creatinine ratio, and determinants of elevated levels were assessed by multivariate analysis.
RESULTS: Diabetes, compared to hypertension, was a more powerful determinant of elevated Cys C and Cr levels in the very old (age >or=80 years), whereas the impact of hypertension was more pronounced in the younger group (age <80 years). The prevalence of microalbuminuria among diabetic subjects was 29.7%, and 15% had elevated Cr levels, whereas the prevalence of elevated Cys C levels varied considerably depending on whether adult or age-adjusted reference limits were used (64.7 vs. 21.4%). In 64.1% of diabetic subjects with elevated Cys C levels based on age-adjusted reference limits and in 48.2% of subjects with elevated Cr levels, microalbuminuria was absent.
CONCLUSIONS: The impact of diabetes on renal impairment changes with increasing age. Serum markers of glomerular filtration rate and microalbuminuria identify renal impairment in different segments of the diabetic population, indicating that serum markers as well as microalbuminuria tests should be used in screening for nephropathy in diabetic older people. The appropriate reference limit for Cys C in geriatric clinical practice must be defined by further research.